The proper response to off-topic nodes is to not approve them. To approve a node is to approve it as on-topic in the section to which it was posted. If it's not on topic, don't approve it. You make the point that Seekers of Perl Wisdom should only contain questions about Perl. You're right (within a range of tolerance for slightly-off-topic posts). So don't approve non-Perl questions into SoPW. That's what the approval system is there for. If a node gets approved that shouldn't be, consider it for unapproval.

Reaping is an inappropriate action in response to an off-topic node. This is documented in the text that every monk with moderation priviliges should read: What is consideration?. Just because a handful of people jumped on the reaping bandwagon before people who are familiar with documented site policy had time to vote to keep the node doesn't mean that they were right. They just took the easy response to a consideration; agree with the motion even if the motion might disgregard documented and established site policy.

Remember, reaping just takes four quick reap votes (with fewer than 2 'keep' votes) and a negative node reputation. The rest is completely out of Janitors' hands; it's automated. But the act of reinstating a reaped node requires the act of one of the gods. The fact that the node you've mentioned got reinstated should tell you that the gods felt strongly enough about the inappropriate action to take the unusual measure of manually undoing the automated process that you set in motion with your consideration.